This Research Report will look specifically at the sill plate requirements according to the 2009, 2012, and 2015 International Residential Code (IRC) and International Building Code (IBC) and clarify if a sill plate is required in the following conditions:

This report discusses ways of increasing the energy efficiency requirements of the building envelope within the context of the requirements of the 2009, 2012 and 2015 International Residential Code (IRC) and IECC forceiling insulation and truss heel heights.

To make the house as energy efficient as possible, we used closed-cell spray foam to fully fill the 3 1/2-inch stud cavities, and 1 1/2 -inch-thick foil-faced polyisocyanurate foam on the exterior to create a thermal break.

When comparing the energy efficiency of cold-formed steel and wood components, the R-value and U-factor are a good place to start.

The R-value measures thermal resistance; it is the inverse of the time rate of heat flow through a building thermal envelope element from one of its bounding surfaces to the other for a unit temperature difference between the two surfaces.

The U-factor measures thermal transmittance, the coefficient of heat transmission (air to air) through a building component or assembly, equal to the time rate of heat flow per unit area and unit temperature difference between the warm side and cold side air films.

The exception to IRC Section R602.3.2 allows for the use of a single top plate in a wood stud wall if the design meets specific requirements.

By cutting the volume of lumber in the top plate in half, a single top plate allows more space for insulation and can reduce thermal bridging through the lumber, which increases the thermal efficiency of the wall system.

When trusses are centered over the studs with a tolerance of not more than 1", the stud spacing can be increased to 24" o.c., which removes more lumber, improves energy efficiency and still provides a continuous load path.

To determine if the use of a single top plate is beneficial, a number of factors must be weighed.